The present invention relates to caffeine dosage forms prepared as aqueous solutions of high levels of caffeine buffered to a pH at which the taste of the caffeine can be effectively masked. In particular, the present invention relates to the use of niacinamide and nicotinic acid as caffeine co-solubilizing agents to provide high concentration caffeine solutions with improved taste that are capable of being effectively formulated with taste-masking components. The present invention also relates to methods for making the buffered caffeine solutions.
Oral caffeine dosage forms are desirable for use as over-the-counter stimulants that can be prepared in the form of breath sprays or breath drops. As a central nervous system stimulant, the administration of caffeine in combination with analgesics and topical anesthetics increases the analgesic or anesthetic effect. Therefore, aqueous oral dosage forms of caffeine with these ingredients would be desirable to provide a product for the temporary relief of toothache or gum inflammation until a dental professional could be consulted.
Caffeine, however, has limited water solubility. This is evident from U.S. Pat. No. 5,382,436, which discloses topical caffeine compositions for use in the treatment of Herpes virus infections. From 8 to 12 percent by weight of caffeine is applied in the form of a dispersion in a topical excipient. This is but one known end-use application for which aqueous caffeine solutions of higher concentration would be desirable.
The acid addition salts of caffeine with citric or hydrochloric acid have significantly greater water solubility. However, the acid addition salts also have an unpleasant taste that is virtually impossible to mask in a commercially practical manner.
Unpleasant tastes are ordinarily masked with an artificial sweetener such as aspartame in combination with flavoring agents. However, solutions of caffeine hydrochloride and caffeine citrate at dosage-effective concentrations have pH's far too low, typically 2.0 and lower. The solutions cannot even be buffered for compounding with aspartame and flavoring agents, which are hydrolytically unstable at these pH's and degrade to reveal the unpleasant taste of the caffeine acid addition salt solution.
There exists a need for higher concentration caffeine solutions in water at pH's acceptable for formulation with taste-masking ingredients.